Design
Engineering
objectives should
be focused towards achieving the most efficient and effective means
toward a conditioned space
that is
within the "Human
Comfort Zone, " and at an affordable investment 'payback' period."

The above
comfort
zone was found
to be acceptable to 90% of test subjects drawn from a range of age
groups and
genders, with work and life-styles involving varying levels of activity
and
clothing. An air conditioning system that establishes and maintains
indoor
conditions within this zone will provide thermal comfort. It will
produce a
neutral sensation, occupants will feel
neither too hot
nor too cold. Above chart and findings From: Home Energy Magazine
Online
September/October 1996) Sizing Air Conditioners: If Bigger Is Not
Better, What
Is? by John Proctor
and Peggy
Albright
---------------------------------------------------------------------------------------------

If
you
over pay for over
capacity equipment, --you will be paying more every month and will not
be as
comfortable as you would sizing it right to also achieve the
appropriate
humidity levels. You must know & record the
operating feet per minute
(FPM)
velocity & the CFM to each room & the Total CFM airflow!
When a typical HVAC contractor quotes the efficiency of the Air
Conditioning
equipment's SEER & Btu/hr, and leads you to believe the new
equipment will
automatically deliver that SEER efficiency & Btu/hr rating, think
again.
Typically, --installed equipment only operates at 55% to 70% of rated
capacity.
Oversized equipment is the worst combination there is because the duct
system
airflow and heatload on the cooling coil are often way off what is
required!

It is important to understand that "equipment ratings are only the
'potential efficiency' of that component of the system under perfect
conditions." Over half of the system’s efficiency depends on
correct equipment sizing run-time,
on the duct system sizing, i.e., on the quality of the complete
field-installation!

SEER

7
SEERor less

8
SEER

9
SEER

10
SEER

12
SEER

13
SEER

'Max' condenser air temp 'delta-T'

30

27

26

18
to 25

17
to 23

ave.
less

Max
temp drop 'across' E-Coil

20

22

24

26

ave.
more

ave.
more

'Max' SA/Return Entering Air 'Delta-T'

35

32

29

27

ave.
less

ave.
less

The Supply Air &
the Entering Return Air delta-T, - tends towards less & less as the
SEER goes higher,
therefore, dehumidification could become more difficult at the highest
SEER levels. The EER & SEER
levels
widen, as SEER sky rockets.

Especially
if your system is oversized or there are a lot of low AC load days use
an adjustable differential room TH.
TH
Differential:Differentialis defined as
the difference between the cut-in and cut-out
points as

measured at the thermostat
under specified operating conditions. For example, if the thermostat
turns

the
COOLING EQUIPMENT on at 78-F & OFF at 76-F that is a 2 degree
differential setting; one has a 4-F adjustable differential. This is a
good way to control high humidity problems & also improve SEER
performance.

What you want & need is right sized equipment operating at
its
optimal ratings within varying conditions, for your optimal comfort
and
savings.

When considering initial cost and pay-back period, -- is there too much
emphasis on ultra-high seer-ratings when considering the most effective
engineering and marketing path towards achieving the most affordable
"Human Comfort Zone" Goals?

"A
lower
cubic feet per minute (cfm) airflow when air is at 50% Relative
Humidity or
below, will condense and absorb a larger portion of the air's latent
heat." With a properly sized system coupled with a properly adjusted
TXV
the system will better adjust to varying conditions.

I
believe
that optimal efficiencies under variable latent heat loads could be
effectively
achieved through the use of computerized engineering.

The
total
latent and sensible evaporator heat load needs to be optimized at your
normal
operating conditions. This will also optimize the condenser's
heat-load.
It is best to have the supply air and return air near the ceiling where
the
warmest air is located.

Come
on
engineers, consumers need a wholly variable system to achieve optimal
efficiency performance when functioning in variable humidity
conditions. HVAC
company engineers can do it, therefore the companies need to get them
on the
market in the proper climate zone areas and at reasonable price levels.
This
computerized control system AC would have to be sized to the
combined
latent and sensible heat load targets (78ºF/50RH) and the cubic
foot volume of
air changes that we would like per hour. This would need to be
performed
accurately to achieve the requisite run time and our
combined
comfort zone and unit efficiency goals.
Air Temperature Drop through Evaporator Coil

A
graphic illustration of how the latent
heat capacity of the DX coil "increases with the increase in
room
relative humidity, and the total condenser load also increases
proportionally. Total system capacity to remove heat in Btu/hr
increases above
the manufactures' ratings which are at 50%
RH when the
Relative Humidity is much higher. Total
Heat (Enthalpy) is the total heat
content of the air and water vapor mixture. It is the sum of both
sensible and
latent values, expressed in Btu per pound of air.

With "a properly
sized
system," thoroughly sealed duct system, and proper evaporator heatload
airflow you will have consistent optimal nominal heat absorption
removal
capacity, coupled with requisite longer run-time cycles. I believe that
optimal
efficiencies by using a variable ratio latent/sensible heat loading,
could be
effectively achieved through the use of computerized system control
components.

Finding out which metering
device the system has without physically looking.

If you do
not know whether the metering device is a TXV or orifice?

Hook up your manifold gauges, block off considerable condenser air intake. If the suction pressure starts rising, you have a piston, or a cap tube. If only the high side goes up, you have a TXV.

If it is a piston, get the CFM airflow correct first, then use the superheat method to charge it.If it is a TXV, subcooling is the way to charge it, but check the Superheat to verify the TXV is holding within specs.

VRF systems
offer
a year round
solution to indoor climate control with unrivalled flexibility and
energy efficiency.

EXVs
- Electronic Expansion Valves -
Control system for heat pump/air-conditioning system for improved
cyclic
performance

The
microprocessor-based control system optimizes efficiency
of the ON/OFF cycle by shutting the expansion valve fully closed at the
beginning of each OFF cycle to maintain system pressure differential.
At the
beginning of each ON cycle the expansion valve is opened to an initial
larger
than average of three openings to allow the system to quickly reach
steady
state operating levels. Thereafter, the valve opening is reduced to an
average
of the last three steady state settings. After a predetermined time,
control of
the valve opening is passed to an adaptive control algorithm which
adjusts the
valve setting for optimized performance during steady state.

The Digital Scroll compressor delivers excellent seasonal energy
efficiency
(SEER). The SEER advantage becomes even greater for a tandem
configuration.
When both compressors are operating, the example system has a high EER
of 11.3
and at 50% capacity, when only one compressor is operating at full
load, the
compressor operates at a high EER of 11.3 too. The operating range for
a single
Digital Scroll is from 10% to 100% and in a tandem configuration is
from 5% to
100%. Wide operating range ensures fewer start-stops on the compressor.
Fewer
start-stops ensure higher system performance. Coupled with two speed
condenser
fan motors!

S
-
Net System

S-
Net is the
Samsung proprietary "system monitoring" program. The software can be
used to monitor the functioning as well as the health of the system -
pressures
and temperatures at all key points in the air-conditioning system. Each
indoor
unit can now be controlled remotely through this software. S - Net is
available
in both RS232 protocol and also TCP/IP. It is now easy to monitor the
health of
an air-conditioning system through the Internet, from a remote
monitoring site.
Figure 7 shows the S- Net cycle monitoring screen. Figure 8 shows the
S- Net
remote controlling screen.

It is better to slightly undersize than to over size, as proper sizing
results
in gains in run time and latent moisture removal. Short-cycling wastes
energy
in obvious ways, start-up uses extra power, it also takes at least 5
minutes
for the unit to reach its cooling capacity.

These
are major
Problems with most Manufacture's Ratings' Data

Air
conditioners
selected based on standard indoor conditions of 80°F Dry Bulb (DB)
with 50%
relative humidity (which is the standard ARI capacity rating condition)
will be
incorrectly sized for 76°F Dry Bulb. Unfortunately, many of the major
manufacturers' provide
information only at 80°F.It
would be a great improvement if the
manufacturers' provided
tables that presented the sensible and latent capacities at 76°F
Dry Bulb for a
variety of indoor humidities.

There is more to the
"System
Btu/hr Capacity Ratings in respect to the conditioned air space," than
meets the eye. "It all depends on what is included or excluded in the
capacity ratings in respect to motor heat Btu/hr that does nothing to
reduce
the total heatload of the conditioned space air." Motor heat is a
factor
to be dealt with, perhaps more so on the smaller units. I will list the
formulas and illustrate the impact of the motor heat from the three
motor
sources.

Some possible Factors to consider when figuring the actual conditioned
space
Sensible Heat-Load to be removed and the
variable
Latent Heat-Load to be removed.

Youcan use the
high-side (SCT) Saturation
Condensing Temperature on your manifold gauge's dial, minus the
outdoors-ambient Temperature; the difference gives you the condenser
temp-rise
or temp/split. There is NO excuse for not utilizing this important
diagnostic
check. Always use an
accurate volt meter
and amprobe to make sure you are not overloading the compressor's
Wattage
Service Factor and check the compressor discharge line to see that it
is under
225-F.

First,
figure the 'rated' gross capacity of the condensing unit. To determine
the
"Gross BTUH Heat Ejection" of the outdoor condenser: New Data = Let's
take the total 'Watts' from the data sheets on an 17,500-Net-BTUH Heil
condenser with a 2-ton DX evaporator coil with a TEV/TXV refrigerant
control.

Take
the "listed
watts" of the compressor and Condenser fan and multiply that wattage by
the Power Factor, they used to use 0.90, then times 3.413 to get the
BTUH heat
additive of the motor, then add the listed BTUH of the condenser to
that
figure, and then divide by the condenser's CFM. Multiply that figure by
1.08 to
get the temperature rise.

For
the
uninitiated, Delta-T is the
difference between the air temperature
entering and
leaving the outdoor AC condensing unit. This is a good diagnostic check
because
it measures the latent heat of condensation as well as the sensible
heat
absorbed by the vaporizing refrigerant in the indoor evaporator coil.
I'm
betting when you find out approximately how many BTUH that the AC
system is
actually transferring outside, you may be shocked by how far it is
below its
BTUH rating.

His
condenser
usually has a 10-F temp delta T, the evaporator appears to be under CFM
heat-loaded or, it has an unbalanced heatload on the DX coil's
circuitry
allowing liquid refrigerant in the return line causing the TXV sensing
bulb to
reduce the refrigerant flow thus reducing the DX coil's heat absorption
capacity.

The
probable cause is "an unbalanced airflow/heatload through the
evaporator coil. "I have a Thermo Pride OL 11 oil furnace. Those
oil
furnaces have a very large round heat exchanger that goes to near the
top of
the furnace, --due to a low basement ceiling the DX coil sets perhaps
illegally
close to the heat exchanger causing a few of the coil's circuits to be
under
heatloaded. Since the liquid refrigerant is not completely evaporated
it will
cause the outlet line that the TEV sensor bulb is on to be too cold and
the TEV
will shut-down the flow, which greatly reduces the BTUH
capacity of the
DX coil and the system. On piston refrigerant control systems, they
may
flood back liquid which could damage the compressor, unless the system
is way
under-charged. Thermo Pride could install airflow turning vanes just
above the
heat exchanger to funnel the air directly into the DX coil, instead of
most of
the airflow hitting the bottom of the DX's drain pan
causing extreme turbulence
back-pressure and an imbalanced DX coil circuitry heatload!The
chart split listed
below is at Condenser Design conditions: Indoor Return Air 80-F dry
bulb 67-F
Wet Bulb or 50% Relative Humidity as you go up to 99% RH the condenser
split could
increase by up to 6-F; down as much as 4-F at a low humidity of 55-F
Wet Bulb.
Do your own figuring
based on this formula. Motor BTU/hr additive =
Watts X's
PF x's 3.413 for Btu/Watts additive added to rated BTUH, divided by
condenser
fan CFM X's 1.08 = condenser Temp-Split. Get the Motor
Power
Factors (PF) of the compressor and fan motor from the manufacturers.
Some
of the temp-split figures need correcting, will do ASAP. Some Splits
rounded.

Do your
own figuring based on
this
formula. Get the Motor Power
Factors (PF) of the compressor and fan motor from the manufacturers.CONDENSER
TEMP-SPLITS 12-SEER
units - Comfortmaker®| Heil® | Temp
Star® - used 0.88
Motor Power Factors

To figure this; units pressure
chart, the Temps, instead of IWB the %RH, & CFM, For
users, No
gauges required, to check if your A/C is near specs!However,
the temperatures & indoor
humidity make a big differenence in the condenser split.(Airflow
with a proper heatload on the evaporator, is key!) Make that outdoor
condenser WORK by putting a high heatload on the indoor evaporator coil!

Take the both the indoor Supply Air & Return Air DB, WB or
%RH , too! If you have an accurate
airflow CFM, I can Ballpark the BTUH your A/C or Heat Pump
is delivering in the cooling
mode.

==============
A modern 2-ton 13-seer system would produce around .70 of
per-ton or
8,400-Btu/hr, however at 70% Relative Humidity its capacity would
increase to
around 1.1 per-ton or 13,200-Btu/hr or over half of the 2-tons would be
used
for the latent heat-load. "That is around a 36%
increase
in latent capacity" and a 36% reduction in sensible capacity, --due to
a
higher humidity.

There are four main factors to humidity control. These are related to
equipment
selection and installation and the effects of the performance of the
four
equipment factors. The Four Factors are: evaporator coil
selection, airflow, refrigerant control device, and
superheat setting of
the
refrigerant cycle.

Proper duct sizing and location is
important. Most older homes need reduced
ambient
(outside) air infiltration and more effective use of vapor barriers,
coupled
with adequate insulation. Windows and doors are special areas to work
on. My
upstairs windows around the pulley wheels for the weights, allowed air
to blow
through almost unrestricted from the attic area both winter and summer.

Air
Flow

When it comes to
airflow, the laws of
physics apply. Air follows the
line of
least resistance. So many of the duct systems are poorly designed that
ductwork
problems can seriously curtail proper system performance. These factors
usually
show up in uneven temperatures through the conditioned area. In
addition,
airflow across the cooling coil can affect humidity removal. Too much
air will
result in poor dehumidification. Too little air can cause the registers
to
sweat. The right amount of air is usually between 325 CFM and 400 CFM
per ton.
Lower airflow will produce increased humidity removal, but compromises
sensible
heat removal. Finding the right air flow and run time balance can
eliminate
most of the comfort zone humidity problems.My scan of my
doctored Thermopride
OL 11 "Oil
Furnace"Graphed
Blower-Curve-Chart
(Same as my brother's Oil furnace)Thermopride
OL 11
Graph ipg
image- Thank you Dave Staso, CA. for
the better expandable image! "After it loads Right click "Show Original Images" -
Move cursor arrow over graph - Click +
when 'over graph' for expanded image," then print on the highest
quality setting.
Notice at 700-RPM with a quarter 1/4HP motor, I checked his actual
airflow at less than 300-CFM (no appreciable duct air leaks). The graph
shows 5.24" SP.

Now, we switch to a 1/3HP motor @800-RPM, the graph shows 6.85" SP
& only 400-CFM, not nearly enough airflow for 1.5-Ton of cooling.
Therefore we have to raise the evaporator coil 6" above the furnace on
rails & then check the airflow. Eliminating that restriction using
a 1/3HP motor, hopefully that will be adequate at +800-rpm & say
+5.5" SP & +700-CFM. Formula:
SP2= (SP2/SP1)2 X's SP1

Condensation
forming on supply air diffusers or registers can be caused by
humid attic air flowing to the register - due
to lack not sealing off the attic air & insulating it properly.

Refrigerant Control Device

The device used to make a cooling coil
evaporate refrigerant and thus
absorb
senile heat and latent heat of humidity is called a Thermostatic
Expansion
Valve refrigerant control. The most effective refrigerant metering
control in
this application is "a external equalized &/or for extreme variable
temperature conditions, a balanced port (TEV/TXV) expansion valve." The
expansion valve provides consistent performance over a wide range of
conditions
that exist in any home. Without an expansion valve the entire system
performance is compromised. Adding an expansion valve to an existing
system can
often improve performance, reduce operating costs, and extend the life
of the compressor & overall system.

R 410a Evacuation
Requirements

Too
many do not
properly
purge & evacuate contaminated
central air conditioning systems.

The
Triple Evacuation Method is normally done on refrigeration systems,
R-410a systems require it on central air
conditioning systems:

First,
remove any valve cores with a special valve core remover this
will
speed up the evacuation time. Back service valves two turns off their
back seat.

1)
Re-claim unit charge (Recover all the refrigerant)

2) Charge
system to 150 PSIG with dry nitrogen and leak test

3) On
contaminated systems replace the filter dryers. Then Repair all
leak(s)

4)
Evacuate system to 500 microns valve off & see if it holds 500
microns for ten minutes, if it holds, break
the vacuum with
dry nitrogen

5)
Evacuate system to a deeper 400 microns, valve off vac pump, &
again break the vacuum with
dry
nitrogen

6)
Evacuate system to 400 microns and & then Check to see if it holds.
(Recharge with fresh
clean refrigerant)

7) Check
to see if the Supply and Return air ducts were correctly sized &
sealed by the original installer.

If a vacuum pump will not evacuate a system below 1500 microns there is
a problem with the pump itself, a leak in the system, or moisture in
the system. Moisture is most likely because water vaporizes at
1500 microns.

Many HVAC
contractors will consider this excessive time & effort
for contaminated
residential
air conditioning systems, however it is a must for low temp
applications.

The
“micron” is a metric unit of measure for
distance. The micron is a unit of linear measure; one micron equals
1/25,400ths
of an inch. Modern high capacity vacuum pumps help speed up the
evacuation process.

When
a system has been evacuated below 500 microns, the pump is valved-off
with the micron gauge connected, if the vacuum rises to 1500
microns and stops, there is moisture remaining in the system. If it
rises above 1500 microns & continues to rise there is a leak. You
should allow at least 15 minutes after the pump has been shut off an
accurate micron gauge reading. When a
system will not evacuate below 1500 microns there is either a lot of
water or there is a system leak.
========================

Superheat -
Controlled by TXV Metering Devices

One
factor that is often overlooked in trying to increase
humidity removal is the the superheat of
the suction
gas. Superheat can often be out of design conditions and the system
seems to
work fine. A five degrees warmer coil temperature can reduce humidity
removal
by 20% or more. Correct TXV adjusted superheat for optimal latent
removal
should be between 5-F and 7-F degrees at the coil. The best time to
adjust the
superheat is on hot summer days, under normal HUMIDITY load conditions
75-F
indoors
strive for 55-F degree discharge air or 20 + degree drop. Humidity levels & CFM airflow
levels determine the indoor latent & sensible SA/RA variable
temperature split. (Using only TXV
metering devices with external equalizers & balanced ports' for
extreme variable weather conditions, is compliant with best practices.)

If
any of the above factors are not
correct you can expect that humidity problems will occur. Other factors
can
affect the humidity levels. The way the house was built — the number of
people that live there and the life style of the occupants. The
correction of
humidity problems in any residence may be accomplished by applying the
above
factors. This is why it is essential that you find a company that you
can trust
to solve your humidity problems. if
neglected,
humidity problems only get worse.

In
my opinion all the components of
air conditioning systems should be engineered and specially designed
for the
climate zone conditions where they will be shipped and used.

In
humid climate areas, the use
of a dehumidistat and variable speed
programmable
indoor blower motors that use half the electricity of conventional
motors could
be used. Also, ask your Utility company
about their
"high efficiency Rebate Program," these programs can add to your
energy cost savings.

Arid
climates can use a higher
temperature operating oversized coil, coupled with 450-cfm or more, per
Btu/hr
ton of cooling, -- cycling through the evaporator coil along with a
lower rated btu/hr compressor to condenser
ratio.

There
ought to be a code requiring
every manufacturer of an airhandler or furnace to provide capped taps
ahead of the
evaporator coil and ahead of the blower for easy static pressure
testing
access.

All
air conditioning condenser
manufacturers' should publish the CFM and normal temperature rise range
across
the condenser coil, so that the service tech's can measure the heat
transferred
from the evaporator coil. Most high efficiency units will have
temperature
degree rises between 18 and 25ºF. Older lower SEER condensers can
have
temperature rises up to 28 or more degrees.

Such
temperature rise data provides a
guide to the actual heat transfer by the evaporator coil to the outdoor
condenser coil, and therefore also, whether the proper design amount of
(cubic
feet per minute) CFM of indoor air/per ton of cooling
Btu/hr, is
passing through the heat absorbing -- cooling coil.

Most higher efficiency units are designed to
operate at
higher evaporator coil temperatures which results in less temperature
drop,
also the high outside and inside humidity levels will put a heavy
latent
heat-load on the evaporator coil will delay the conditioned area's
temperature
drop.

You
may also have too much outside air
infiltration into your home, check it out and reduce it, because warmer
high
humidity air will overload the evaporator coil with latent heat removal
with
the result being little if any reduction in humidity levels and no
lowering of
the actual sensible temperature readings in the conditioned areas.

In high humidity
climates everything in the home is loaded
with the latent heat of moisture. Humid air contains a lot of
heat-loaded
vapor. Some moisture is airborne but most of it resides or hides in the
bricks,
wooden furniture, carpeting, walls, and the concrete floors we walk on,
etc.
Dish washers, clothes washers and taking hot showers, etc., all add a
lot of
moisture to the air and to home materials.
This latent moisture in the conditioned area is vaporizing in the air,
and as
it is being conditioned it gives up its latent heat to the evaporator
coil's
liquid refrigerant causing it to boil into the heat absorbing
refrigerant vapor.
That heat-loaded vapor is then sucked back to the compressor where it
is
compressed into a high temperature gas in the condenser coils, where
the
outside air cooler outside air cools it below its condensing
temperature point
causing the vapor to condense into a liquid.

====================== DISCLAIMER:

I
do NOT
assume any responsibility for how anyone uses the information on my Web
pages.
All HVAC/R work should always be done by a licensed Contractor! This
information is only placed on these pages for your understanding &
communication with contractors & techs.

This
information is for the edification of contractors and techs.I am NOT liable for what you do,
you are liable for what you do!
- Darrell Udelhoven